The simultaneous implementation of a comprehensive background check (CBC) and misdemeanors violence policies (MVP) were not associated with a net change in the firearm homicide rate over the ensuing 10 years in California. The decrease in firearm suicides in California was similar to the decrease in nonfirearm suicides in that state. Results were robust across multiple model specifications and methods.

Abstract
In 1991, California implemented a law that mandated a background check for all firearm purchases with limited exceptions (comprehensive background check or CBC policy) and prohibited firearm purchase and possession for persons convicted within the past 10 years of certain violent crimes classified as misdemeanors (MVP policy). We evaluated the population effect of the simultaneous implementation of CBC and MVP policies in California on firearm homicide and suicide.

Methods
Quasi-experimental ecological study using the synthetic control group methodology. We included annual firearm and nonfirearm mortality data for California and 32 control states for 1981–2000, with secondary analyses up to 2005.

Results
The simultaneous implementation of CBC and MVP policies was not associated with a net change in the firearm homicide rate over the ensuing 10 years in California. The decrease in firearm suicides in California was similar to the decrease in nonfirearm suicides in that state. Results were robust across multiple model specifications and methods.

ConclusionsCBC and MVP policies were not associated with changes in firearm suicide or homicide. Incomplete and missing records for background checks, incomplete compliance and enforcement, and narrowly constructed prohibitions may be among the reasons for these null findings.

A few of the findings in this report, as written up by Kyle Wintersteen

1. Armed citizens are less likely to be injured by an attacker:
“Studies that directly assessed the effect of actual defensive uses of guns (i.e., incidents in which a gun was ‘used’ by the crime victim in the sense of attacking or threatening an offender) have found consistently lower injury rates among gun-using crime victims compared with victims who used other self-protective strategies.”

2. Defensive uses of guns are common:
“Almost all national survey estimates indicate that defensive gun uses by victims are at least as common as offensive uses by criminals, with estimates of annual uses ranging from about 500,000 to more than 3 million per year…in the context of about 300,000 violent crimes involving firearms in 2008.”

3. Mass shootings and accidental firearm deaths account for a small fraction of gun-related deaths, and both are declining:
“The number of public mass shootings of the type that occurred at Sandy Hook Elementary School accounted for a very small fraction of all firearm-related deaths. Since 1983 there have been 78 events in which 4 or more individuals were killed by a single perpetrator in 1 day in the United States, resulting in 547 victims and 476 injured persons.” The report also notes, “Unintentional firearm-related deaths have steadily declined during the past century. The number of unintentional deaths due to firearm-related incidents accounted for less than 1 percent of all unintentional fatalities in 2010.”

5. Gun buyback/turn-in programs are “ineffective” in reducing crime:
“There is empirical evidence that gun turn in programs are ineffective, as noted in the 2005 NRC study Firearms and Violence: A Critical Review. For example, in 2009, an estimated 310 million guns were available to civilians in the United States (Krouse, 2012), but gun buy-back programs typically recover less than 1,000 guns (NRC, 2005). On the local level, buy-backs may increase awareness of firearm violence. However, in Milwaukee, Wisconsin, for example, guns recovered in the buy-back were not the same guns as those most often used in homicides and suicides (Kuhn et al., 2002).”

6. Stolen guns and retail/gun show purchases account for very little crime:
“More recent prisoner surveys suggest that stolen guns account for only a small percentage of guns used by convicted criminals. … According to a 1997 survey of inmates, approximately 70 percent of the guns used or possess by criminals at the time of their arrest came from family or friends, drug dealers, street purchases, or the underground market.”

7. The vast majority of gun-related deaths are not homicides, but suicides:
“Between the years 2000-2010 firearm-related suicides significantly outnumbered homicides for all age groups, annually accounting for 61 percent of the more than 335,600 people who died from firearms related violence in the United States.”